Temporary hemiepiphyseal arrest using a screw and plate device to treat knee and ankle deformities in children: a preliminary report

Abstract

Purpose: Traditionally, angular deformities are treated by means of osteotomy. In patients who are skeletally immature, this major intervention can be avoided by influencing or guiding the growth of the affected physis. Recently, a new device was presented as an alternative to the widely used Blount staple. Stevens developed a technique using a two-hole, non-locking plate with two screws to perform temporary hemiepiphysiodesis in children. We studied the effectiveness of this new device in correcting angular deformities in children even younger than 5 years of age.

Methods: We evaluated our first series of 11 patients (17 eight-Plates) who underwent treatment for angular deformities of various origins and were followed to completion of correction. The average age at hemiepiphysiodesis was 10 years and 2 months (age range 4 years and 11 months-13 years and 8 months). The device was inserted in the lateral distal femur (two cases), the medial distal femur (eight cases), the lateral proximal tibia (two cases), the medial proximal tibia (four cases), and the medial distal tibia (one case).

Results: The eight-Plate was inserted for an average of 9.5 months (range 5-13 months). The joint orientation angles and the mechanical axis improved in all patients, with the exception of one 13-year and 8-month-old boy with a resected osteosarcoma and a compromised growth plate. In valgus cases (12 limbs, 13 eight-Plates), the mechanical axis deviation improved by an average of 30.7 mm (range 13-55 mm). In varus cases (four limbs, four eight-Plates), the mechanical axis deviation improved by an average of 38.8 mm (range 0-74 mm). No hardware failures, extrusion, growth arrest, or other complications were observed. None of our patients required an osteotomy or repeat eight-Plate insertion.

Conclusions: We consider the eight-Plate to be an ideal tool for treatment of angular deformities in growing children. It allows for precise insertion and is reliable. It is also less likely to extrude like the Blount staple.

Figures

Fig. 1

a Photograph shows two sizes of the eight-Plate Guided Growth System: 12 and 16 mm. The eight-Plate kit includes three sizes of cannulated screws (16, 24, and 32 mm). b Photograph shows the complete eight-Plate set (clockwise from top): a 3.2-mm cannulated drill bit, a 21-gauge needle, two 1.5-mm wires with 1.2-mm threaded tips, a screwdriver, four eight-Plates, ten cannulated screws, and a drill-guide. New instrumentation kits include a 3.2-mm cannulated step drill and a guide to limit penetration to 5 mm. c Guide wires, 21-gauge needle, cannulated screws, and an eight-Plate. The cannulated screws are inserted over the guide wires. The 21-gauge needle provides temporary fixation. d Photograph shows that the screws are able to pivot within the eight-Plate (greater than 45° of rotation is possible)

Fig. 2

Application of the eight-Plate. a Anteroposterior view radiograph shows a 1.5-mm Kirschner wire being used to position the eight-Plate so that it straddles the physis. b Lateral view radiograph shows that the position of the eight-Plate is monitored so that it is not positioned too anterior or posterior in the sagittal plane. c Anteroposterior view radiograph shows two guide wires with threaded tips inserted in the two holes of the eight-Plate. Cannulated screws are then inserted over the guide wires. d Anteroposterior view radiograph shows the final position of the eight-Plate and screws. The longer 32-mm screws depicted here are preferred over the shorter screws, especially when inserted in the metaphysis

Fig. 3

A 5-year and 7-month-old boy with bilateral insertion of an eight-Plate in the medial distal femur. a Preoperative anteroposterior view radiograph shows significant bilateral mechanical axis deviation (MAD) of 20 mm. b Anteroposterior view radiograph shows the patient after undergoing 10 months of treatment. The patient has slight bilateral over correction to 4 mm medial MAD

Fig. 4

A 13-year-old girl with valgus deformity treated with an eight-Plate in the right distal medial femur. a Anteroposterior view radiograph shows the right limb with significant mechanical axis deviation (MAD) of 49 mm lateral. b Anteroposterior view radiograph shows the patient after 10 months of treatment. The patient has a slight over correction to 6 mm medial MAD

Fig. 5

Change in the mechanical axis deviation (MAD) for 17 eight-Plates (16 limbs) measured preoperatively and postoperatively. The average normal MAD is 4.1 ± 4 mm medial [12]

Fig. 6

Joint orientation angles at the time of eight-Plate insertion and removal. a Mechanical lateral distal femoral angle (mLDFA) of cases in which the eight-Plate was inserted in the distal femur. b Medial proximal tibial angle (MPTA) of cases in which the eight-Plate was inserted in the proximal tibia. c Lateral distal tibial angle (LDTA) of cases in which the eight-Plate was inserted in the distal tibia

Fig. 7

a Photograph shows spontaneous extrusion of a Blount staple in a young child. b Photograph shows the eight-Plate in a 5-year and 6-month-old child. The screws provide better fixation than staples in the partially ossified epiphysis